docs: def to_ascii_bytes(self, filter_func=None):
          """ Attempt to encode the headers block as ascii
              If encoding fails, call percent_encode_non_ascii_headers()
              to encode any headers per RFCs
          """
          try:
              string = self.to_str(filter_func)
              string = string.encode('ascii')
          except (UnicodeEncodeError, UnicodeDecodeError):
              self.percent_encode_non_ascii_headers()
              string = self.to_str(filter_func)
              string = string.encode('ascii')
  
          return string + b'\r\n'